<?php

include_once "errorCode.php";

/**
 * PKCS7Encoder class
 *
 * 提供基于PKCS7算法的加解密接口.
 */
class PKCS7Encoder
{
	public static $block_size = 32;

	/**
	 * 对需要加密的明文进行填充补位
	 * @param $text 需要进行填充补位操作的明文
	 * @return 补齐明文字符串
	 */
	function encode($text)
	{
		$block_size = PKCS7Encoder::$block_size;
		$text_length = strlen($text);
		//计算需要填充的位数
		$amount_to_pad = PKCS7Encoder::$block_size - ($text_length % PKCS7Encoder::$block_size);
		if ($amount_to_pad == 0) {
			$amount_to_pad = PKCS7Encoder::block_size;
		}
		//获得补位所用的字符
		$pad_chr = chr($amount_to_pad);
		$tmp = "";
		for ($index = 0; $index < $amount_to_pad; $index++) {
			$tmp .= $pad_chr;
		}
		return $text . $tmp;
	}

	/**
	 * 对解密后的明文进行补位删除
	 * @param decrypted 解密后的明文
	 * @return 删除填充补位后的明文
	 */
	function decode($text)
	{

		$pad = ord(substr($text, -1));
		if ($pad < 1 || $pad > 32) {
			$pad = 0;
		}
		return substr($text, 0, (strlen($text) - $pad));
	}

}

/**
 * Prpcrypt class
 *
 * 提供接收和推送给公众平台消息的加解密接口.
 */
class Prpcrypt
{
	public $key;

	function __construct($k)
	{
		$this->key = base64_decode($k . "=");
	}

/**
 * 对明文进行加密
 * @param string $text 需要加密的明文
 * @return string 加密后的密文
 */
public function encrypt($text, $appid)
{
    try {
        //获得16位随机字符串，填充到明文之前
        $random = $this->getRandomStr();//"aaaabbbbccccdddd";
        $text = $random . pack("N", strlen($text)) . $text . $appid;
        $iv = substr($this->key, 0, 16);
        $pkc_encoder = new PKCS7Encoder;
        $text = $pkc_encoder->encode($text);
        $encrypted = openssl_encrypt($text,'AES-256-CBC',substr($this->key, 0, 32),OPENSSL_ZERO_PADDING,$iv);
        return array(ErrorCode::$OK, $encrypted);
    } catch (Exception $e) {
        //print $e;
        return array(ErrorCode::$EncryptAESError, null);
    }
}
/**
 * 对密文进行解密
 * @param string $encrypted 需要解密的密文
 * @return string 解密得到的明文
 */
public function decrypt($encrypted, $appid)
{
    try {
        $iv = substr($this->key, 0, 16);
        $decrypted = openssl_decrypt($encrypted,'AES-256-CBC',substr($this->key, 0, 32),OPENSSL_ZERO_PADDING,$iv);
    } catch (Exception $e) {
        return array(ErrorCode::$DecryptAESError, null);
    }
    try {
        //去除补位字符
        $pkc_encoder = new PKCS7Encoder;
        $result = $pkc_encoder->decode($decrypted);
        //去除16位随机字符串,网络字节序和AppId
        if (strlen($result) < 16)
            return "";
        $content = substr($result, 16, strlen($result));
        $len_list = unpack("N", substr($content, 0, 4));
        $xml_len = $len_list[1];
        $xml_content = substr($content, 4, $xml_len);
        $from_appid = substr($content, $xml_len + 4);
        if (!$appid)
            $appid = $from_appid;
        //如果传入的appid是空的，则认为是订阅号，使用数据中提取出来的appid
    } catch (Exception $e) {
        //print $e;
        return array(ErrorCode::$IllegalBuffer, null);
    }
    if ($from_appid != $appid)
        return array(ErrorCode::$ValidateAppidError, null);
    //不注释上边两行，避免传入appid是错误的情况
    return array(0, $xml_content, $from_appid);
    //增加appid，为了解决后面加密回复消息的时候没有appid的订阅号会无法回复
}

	/**
	 * 随机生成16位字符串
	 * @return string 生成的字符串
	 */
	function getRandomStr()
	{

		$str = "";
		$str_pol = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz";
		$max = strlen($str_pol) - 1;
		for ($i = 0; $i < 16; $i++) {
			$str .= $str_pol[mt_rand(0, $max)];
		}
		return $str;
	}

}

?>